Heat the oven to 400°F. Lightly grease eight cups of a standard muffin tin.
In a large bowl, combine the ground beef, egg, panko, onion, 2 tablespoons of the Buffalo sauce, garlic powder, salt, and pepper. Mix gently until combined, taking care not to pack the mixture too tightly.
Divide the beef mixture among the eight prepared muffin cups. Press it in lightly, then spoon the remaining Buffalo sauce over the tops.
Bake for 20 to 25 minutes, until the muffins are cooked through. Let them rest in the tin for 5 minutes before removing.
While the muffins bake, toss the cabbage and carrots with the ranch dressing and chopped chives. Serve the slaw alongside the warm Buffalo meatloaf muffins.